Railway Investigation Report R13C0069
The Transportation Safety Board of Canada (TSB) investigated this occurrence for the purpose of advancing transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.
Bridge failure and derailment
Canadian Pacific Railway
Freight Train 292-26
Mile 172.5, Brooks Subdivision
On 27 June 2013, at 0320 Mountain Daylight Time, Canadian Pacific Railway freight train 292 26, proceeding eastward from Canadian Pacific Railway’s Alyth Yard in Calgary, Alberta, to Medicine Hat, Alberta, derailed 6 tank cars on the Bonnybrook Bridge over the Bow River at Mile 172.5 on the Brooks Subdivision. There was no product loss, and there were no injuries.
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Beginning in the week prior to 27 June 2013, record rains upstream resulted in flooding of the Bow River Basin. On 21 June, the Elbow River and the Bow River peaked. During this period, the volume, speed, and turbidity of the river prevented below-water inspections of the Bonnybrook Bridge. All bridge inspections during the flood were conducted at track level. In addition to formal bridge inspections performed by qualified bridge inspectors, other Canadian Pacific Railway (CP) personnel (i.e., transportation and engineering service employees) observed the condition of the bridge multiple times daily to monitor rail alignment and elevation deviations in order to ensure that no movement was occurring. Based on these observations, CP assessed the bridge as suitable for continued rail operations.
On 27 June 2013, shortly after midnight, CP freight train 292-26 (the train) arrived in Alyth Yard (Calgary, Alberta) from Red Deer, Alberta, with 72 loaded cars and 57 empty cars. At 0204,Footnote 1 westbound CP freight train 675-053, with 166 loaded cars of potash, weighing 24 266 tons and 8283 feet long, crossed over the Bonnybrook Bridge on track P1 into Alyth Yard without incident and without any indication of imminent failure.
At about 0310, after performing some switching for train 292-26 and changing crews, the train departed Alyth Yard on track P2, destined for Medicine Hat, Alberta. The train now comprised two 6-axle, AC4400 HP General Motors locomotives, 62 loaded cars, and 23 empty cars. It weighed 9007 tons and was 5358 feet long.
At 0314, with the train travelling at 9 mph, a train-initiated emergency brake application occurred. The train stopped 22 seconds later. After making the necessary emergency broadcast and notifying the rail traffic controller (RTC), the conductor performed an inspection and determined that 6 tank cars (the 63rd car to the 68th car) situated on the Bonnybrook Bridge had derailed in an upright position. The bridge failed at the Pier no. 2 location, under the 67th and 68th cars (Photo 1). There were no injuries, and there was no loss of product.
The Bonnybrook Bridge is situated in southeast Calgary and spans the Bow River (Photo 2). The bridge is located at Mile 172.5 of the Brooks Subdivision on CP's main line, connecting it with Alyth Yard. The Bonnybrook Bridge is a key element of CP's east–west rail network.
In the vicinity of the Bonnybrook Bridge, there are 2 other bridges:
The derailed cars
Information related to the derailed cars is summarized in Table 1.
|Car no.||Car ID||Car typeFootnote 2||Contents||Date built||Most recent tank test||Load status|
|63||TILX 261251||AAR211A100W1||Ethylene glycol (UN 3082)||January 2005||2005||Load|
|64||NATX 50264||111A100W3||DURASYN 125Footnote 3||September 1989||2008||Residue|
|65||GATX 211363||111A100W1||Flammable liquid, n.o.s. (UN 1993)||October 2012||2012||Load|
|66||CBTX 742965||111S100W1||Flammable liquid, n.o.s. (UN 1993)||December 2012||2012||Load|
|67||CBTX 742912||111S100W1||Flammable liquid, n.o.s. (UN 1993)||November 2012||2012||Load|
|68||TILX 224072||111A100W1||Flammable liquid, n.o.s. (UN 1993)||February 1992||2007||Load|
The characteristics of the products carried in the derailed cars include the following:
The Bonnybrook Bridge was a 465-foot-long, 5-span bridge.Footnote 4 With 4 tracks, this bridge was part of CP's main line, connecting the Brooks Subdivision to the east, and Alyth Yard and the Laggan Subdivision to the west. Traffic over this bridge consisted of about 30 trains per day, not including the switching movements originating from Alyth Yard, which used the bridge.
The bridge, which was oriented at a 58º angle to the alignment of the river and pier, consisted of
The history of the Bonnybrook Bridge is summarized as follows:
All 4 tracks over the bridge were tangent on a 0.217% ascending grade to the east. From south to north, the tracks were
All 4 tracks consisted of 136-pound rail laid on double-shouldered tie plates and fastened with spikes. The rail on track P2 and on the Old Ogden track rested on the bridge timbers and was unanchored. The rail on the New Ogden track rested on the 1969 ballast deck extension and was anchored on treated ties. Track P1 was continuous welded rail (CWR), and the other tracks were jointed rail.
During site examination, the following was noted:
Rainfall and flooding prior to the accident
One hundred fifty mm of rain had fallen west of Calgary near Canmore, Alberta, and Exshaw, Alberta, in a 48-hour period by early morning of 20 June. Sporadic, high rainfalls of up to 20 mm per hour were also recorded. Flash floods and mud slides had occurred in several sections upstream of the Bow River Basin.
Some of the resulting flood damage and flood mitigation strategies by CP and other agencies included the following:
On 20 June, a number of emergency precautions were undertaken by the City of Calgary, including the following:
Note: The data were taken from a river gauge located about 0.8 km upstream of the confluence of the Bow and Elbow Rivers and 7 km upstream of the Bonnybrook Bridge. These data do not account for the flow in from the Elbow River. Both the Elbow River and the Bow River peaked on 21 June.
On 22 June, restricted access and power outages continued to affect a significant part of the downtown core.
On 23 June, evacuation orders were lifted in all areas except the downtown core. Water flow rates in the Bow River and Elbow River were down significantly.
On 24 June, parts of the downtown remained closed and without power. About 80% of C‑Train (public light rail transit) service was restored. Several road closures remained in effect. Most communities were partially or fully reopened, and power was restored to all affected areas by 28 June.
Inspection of the Bonnybrook Bridge during the Calgary flood
During the Calgary flood, water volume, speed, and turbidity prevented underwater inspections of the Bonnybrook Bridge. The bridge inspections were being conducted at track level. In addition to these formal bridge inspections performed by qualified bridge inspectors, CP transportation and engineering service employees were observing the condition of the bridge multiple times daily to monitor for rail alignment and elevation deviations and to ensure that no movement was occurring.
Between 20 June and 24 June, there were 18 bridge inspections (including measurement of water elevation) by CP engineering supervisors. During the height of the flood (21 June), the water level had risen to about 8 inches below the bridge girders (Photo 5 and Photo 6).
Other actions taken in the vicinity of CP bridges during the flood included
Inspection of other bridges during the Calgary flood
During the flood, the City of Calgary conducted the following inspections:
Historical flooding of the Bow River
The Red Deer River, Bow River, Oldman River, and South Saskatchewan River are part of the South Saskatchewan River Basin (SSRB), one of 7 major river basins in Alberta. Severe flooding of the Bow River has occurred several times since the late 1800s (Figure 3) and has included the following events:
The volume of water in southern Alberta Rivers had—in most cases—never previously reached the recorded water flow rates that occurred in 2013. Appendix A shows the estimated peak river flows.
In the week before the flooding, meteorologists were aware that there was the potential for severe thunderstorms and heavy rain in Alberta. Computer models suggested a unique weather pattern that could lead to flooding.
An upside-down weather pattern had taken shape across Western North America earlier that week. “Upside-down” refers to a jet stream pattern in which there are warmer temperatures to the north, as compared to the south.
The jet stream is the roughly continuous corridor of strong high-altitude winds (at the cruising altitude of passenger aircraft) that moves from west to east across the mid-latitudes. The jet stream pattern that dictates the weekly variation in weather has ups and downs (i.e., what meteorologists call “ridges” and “troughs”).
Sometimes, the jet stream pattern gets stuck or “blocked”. This was the condition that took shape across Western North America during the week of 16 June. The large “up”, or ridge, in the jet stream, resulting in record warmth in Alaska and hot weather across parts of Canada's North, blocked a strong dip in the jet stream from moving quickly from west to east. In Figure 4, the “H” represents high pressure, or the “up” in the jet stream, and the “L” represents low pressure, or the “down” in the jet stream.
With the counter-clockwise winds around this low-pressure system, a channel of very moist air was tapped from the Gulf of Mexico and pulled into Alberta. This atmospheric river of water vapour moved north and then east over the foothills and Rocky Mountains, rising, cooling, condensing, and releasing large amounts of precipitation.
In addition, a late but rapid snowmelt at upper elevations of the Rocky Mountains contributed to the flooding.
Canadian Pacific Railway weather forecasting
The Rail Weather Information System (RailWIS) was developed for CP as its weather threat monitoring and warning system. This system had been the railway's decision support tool for extreme hydrometeorological events for many years. Its components includedFootnote 10
Prior to the occurrence (18 June to 21 June), CP had received rainfall and severe thunderstorm warnings from RailWIS. No SWALs had been issued.
Regulatory oversight of railway bridge safety
To manage bridge safety in the manner required by the Railway Safety Management System Regulations, railway companies use a bridge safety management program (BSMP) approach that includes, as a minimum, annual inspection of bridges, determination of safe load capacity of bridges, and conduct of special inspections if weather-related conditions (e.g., floods) or other conditions warrant such inspections.
Transport Canada (TC) has developed the Guideline for Bridge Safety Management in consultation with the railway industry. The guideline was first published in February 2011, with the latest version dated February 2012. The guideline outlines TC's expectations and industry best practices with respect to the railway's BSMP. Shortly after the document was published, railways were asked to submit a phase-in schedule for the development of their BSMP.
TC developed Gap Analysis: Bridge Safety Management Program Implementation, which is an evaluation tool to assist TC inspectors in the evaluation of a railway's BSMP.
TC's bridge program consists of compliance monitoring activities, focusing on the following 4 activities:
TC Rail Safety inspections are generally delivered by the regions. A typical inspection consists of a review of the selected bridge's inspection and maintenance records, followed by a site visit.
TC's regulatory oversight consists of Components A, B, and C, which are defined as follows:
“Component “A” monitoring activities are sampling inspections and audits conducted in support of the Functional Disciplines' Inspection and Audit Programs. Developed annually in accordance with functional specific planning templates/criteria, Component “A” inspection plans utilize statistical sampling methods with environmental scoping risk consideration. Component “A” is a national program, which is administered from HQ and delivered by the 5 regions. For oversight of railway bridges, Transport Canada (TC) Headquarters will select 5 Subdivisions per region per year along with a starting mileage for these Subdivisions. TC Regions will pick 7 consecutive railway bridges from these selected Subdivisions and starting mileages for a total of 35 bridges, including any overhead structure located within the said area of inspection.
Component “B” monitoring activities are the inspections and audits identified during the annual Risk-Based Business Planning cycle (planned before the start of the fiscal year). The objective of Component “B” monitoring activities is to address conditions, activities or issues that have created, or have the potential to create, a risk to safety, and/or Ministerial, Departmental or Rail Safety Program embarrassment, loss of respect/confidence, or financial/time loss.
Component “C” monitoring activities are inspections and audits to issues that arise after April 1 (unplanned at the beginning of the year). The objective of Component “C” monitoring activities is to address emerging issues and provide for opportunity inspections.Footnote 11
Normally, Component C inspections are identified by the Regions and are triggered by
Railway bridge safety management program
CP bridge inspection protocols were based on its Railway Bridge Safety Management Program (RBSMP), effective 14 March 2011. CP developed its BSMP in accordance with TC's Guideline for Bridge Safety Management.
CP maintains its bridge inventory in an electronic database. The database includes all bridge structures with a deck, regardless of length, that supports 1 or more railroad tracks. Other under-grade structures (e.g., tunnels) with a span length of 3 m (10 feet) or more are also included in the database. The bridge data elements include subdivision, mileage, bridge type, number of spans, length of bridge, bridge deck type and material; span number, length, type and components, and year built; abutment type and material; and pier number, type and material.
CP's RBSMP includes the following components:
Underwater bridge inspections
Section 126.96.36.199.3.1 of CP's RBSMP indicates the required frequency of underwater bridge inspections. Specifically, bridge substructures within watercourses and the watercourse bed conditions should be inspected as follows:
Section 188.8.131.52.3.2 of CP's RBSMP identifies the types of underwater inspections. Underwater inspections are performed visually (by eye, photography, or video) or tactilely, using physical or sonar probes. The inspections are performed at appropriate intervals, for the purpose of evaluating the structural condition of substructures and the scour conditions of the watercourse bed. Depending on the waterway and structure conditions, the visual and/or tactile inspections can be routine or detailed. The following types of underwater inspections are identified in this section of the RBSMP:
Section 184.108.40.206.3.3 of CP's RBSMP specifies the underwater inspection frequency, which considers flow rates, susceptibility to scour and flood, and vessel impact. Based on the matrix of factors, the inspection frequencies for the Bonnybrook Bridge were identified as follows:
The Bonnybrook Bridge was classified in this manner because the Bow River flow is high only during the spring, because the pier footings can be clearly seen during periods of low water, and because the bridge had no history of scour.
Section 220.127.116.11.2 of CP's RBSMP indicates that where a bridge may have sustained damage through contact by railway equipment or loads, road vehicles, marine vessels, debris flow, derailment, flood, or fire, an emergent bridge inspection is required. For the Bonnybrook Bridge, an emergent inspection was conducted after the 2005 flood.
Bridge scour is the erosion of soil or other supporting material from around the base of a bridge pier or bridge abutment. Bridge scour is typically caused by the excessive flow of water or ice. There are 2 types of local bridge scour:
The basic mechanism causing local bridge scour is the formation of vortices (a phenomenon known as a horseshoe vortex) at the base of an obstruction (e.g., a pier or abutment). The horseshoe vortex results from the pileup of water on the upstream surface of the obstruction, followed by the subsequent acceleration of the water flow around the obstruction. The vortex action removes riverbed material from around the base of the obstruction. When the transport rate of sediment away from the base region is greater than the transport rate into the region, a scour hole develops.
Bonnybrook Bridge inspections
The bridge inspector assigned to CP's Calgary Division was responsible for conducting annual inspections of the Bonnybrook Bridge. The bridge inspector was also responsible for performing a minimum of 3 cursory inspections per month at this bridge. Inspections were also conducted each time maintenance and repair work was done on the bridge. The bridge supervisor in this division was also a fully qualified bridge inspector, who had extensive training and experience.
The last known detailed tactile inspection of Bonnybrook Bridge had been performed in 1987. The last major Bow River flood had occurred in June 2005. As required by CP's RBSMP, a visual post-flood inspection of the Bonnybrook Bridge foundation was conducted in the low-water annual inspection. The results of the inspection after the 2005 flood indicated that no scour had occurred.
Although multiple visual inspections for surface and alignment deviations were conducted between 20 June and 24 June, the last annual inspection of Bonnybrook Bridge prior to the accident was conducted on 13 September 2012. The condition of each bridge inventory component was assessed using the rating scale in Table 2.
|Component condition rating||Description of condition|
|9||Needs immediate attention|
During the September 2012 inspection, bridge scour was rated as 2 (i.e., good). No other exceptions were noted. The scour rating had been assigned based on observations of the riverbed in the vicinity of the pier and abutments when the water level was low. No substructure action was recommended following the 2012 inspection.
Post-accident examination of Bonnybrook Bridge
Post-accident photographs taken 04 September 2013, when the river level had subsided, show that the upstream 1912 extension had separated from the original masonry block pier (Photo 7 and Photo 8). The river bottom can also be seen in these photographs. During some of the dry months (e.g., September), the foundation of Pier no. 2 can be completely out of the water.
Photo 9 (taken in September 2013) shows a rock bar deposited downstream under the Ogden Road Bridge. Some of the broken-up bedrock deposited at this location had likely originated from under and around Pier no. 2 of the Bonnybrook Bridge.
Post-flood underwater inspection of Bonnybrook Bridge
Underwater inspection of Pier no. 2 of the Bonnybrook Bridge was not possible during the flood, due to the high volume and high flow rate of the silty flood water. However, on 28 June 2013 (after the accident), a bathymetric surveyFootnote 13 was conducted. This survey identified a scour hole on the downstream side of Pier no. 2. The survey images indicated that scour of more than 1 m was present downstream of Pier no. 2, and that much less scour was present around the other piers.
A subsequent bathymetric survey was conducted in late August 2013, when the water had cleared and the flow rate had dropped to normal levels. A sonar (acoustic) survey of the riverbed and the west side of Pier no. 2 was also performed (Photo 10 and Photo 11). A diver was also used to assess the extent of the scour. It was determined that the June flood had created a major scour hole on the west side (i.e., downstream end) of Pier no. 2 and in the river channel between Pier no. 2 and Pier no. 3.
Table 3 summarizes the results of the sonar survey at Pier no. 2. The sonar images for drop no. 2, drop no. 3, and drop no. 4 are presented in Appendix B.
|Sonar drop no.||Depth to riverbed at base of scour (m)||Depth of subduction* (m)||Length of subduction (m)|
* Undercut or erosion depth
The scour or undercut of Pier no. 2 ranged from 33% to 49% of the width of the 3.353-m-wide pier extension.
Emergency response following the bridge failure and derailment
Following the bridge failure and derailment, the following emergency response activities were initiated:
The train consist, which was available from the conductor, provided information on car numbers, car position, AARFootnote 14 car type, commodity, dangerous goods UN number, load/empty status, shipper, consignee, and Standard Transportation Commodity Codes. The Emergency Response Guidebook published by TC, a guidebook for first responders during the initial phase of a transportation incident involving dangerous goods or hazardous materials, was in the possession of train crew members and dangerous-goods emergency responders. The train consist identified the contents of cars 65 to 68 as NA1993, a flammable liquid n.o.s. (not otherwise specified). The 4‑digit product identification number, known as a UN or NA (North America) number, and the hazard class listed on car placards are broad and can encompass many different hydrocarbons that have similar chemical composition but different response requirements. Compressed waybills obtained from the shipper, Imperial Oil, named the product as petroleum distillate.
Neither CANUTECFootnote 15 nor CHEMTRECFootnote 16 were contacted by the CFD for information regarding the products in the derailed cars. The product in the tank cars was readily identified once the material safety data sheet (MSDS) was received from CP. The MSDS confirmed that cars 65 to 68 contained intermediate catalytic cracked distillate, commonly called natural gasoline. Determination of the concentration of hydrogen sulphide took a little longer; this information was learned when the CFD hazardous materials team contacted the product refinery lab.
Once it was determined that the bridge had stabilized, discussion between CP and city emergency responders focused on how to safely remove the cars from the bridge. The cars were removed in the following manner:
The evacuation order was rescinded at 0215 on 28 June, and rail traffic was resumed over the remaining 1969 bridge at 0345.
Train operation was not considered to be a causal factor in this occurrence. There was no indication that a mechanical failure on any of the rolling stock contributed to the accident. The analysis will focus on the bridge failure, bridge inspection and maintenance, bridge scour and emergency response.
As train 292 travelled eastward over the Bonnybrook Bridge, the bridge failed under the train, resulting in the derailment of 6 cars. The bridge failed due to scour, which caused the loss of foundation at Pier no. 2. The foundation failure resulted in the clean separation of the 1912 downstream concrete extension from the original masonry block pier.
The foundations of the original masonry block pier and of both the upstream and downstream 1912 concrete extensions were spread footings on river bottom shale and sandstone. Spread footings were the construction technique of the day. The majority of the pier extension foundation was on shale/sandstone bedrock, with a small portion of the downstream end of the pier extension foundation situated on a clay seam. The bridge had endured several major floods over the past century. This time, however, the intense, unprecedented flood-water flow attacked the shale/sandstone/clay pier foundation, eroding and undermining it. The bridge scour continued to the point where the 1912 downstream concrete pier extension became unsupported and separated from the original masonry pier under train 292, and fell off into the river.
The concrete extension footing, which was connected with reinforcing bars to a false footing around the original pier, likely kept the 1912 downstream concrete pier extension from falling off earlier. The lack of keying or connecting of the original masonry block pier to the 1912 upstream extension allowed the upstream extension to separate cleanly, without further damaging the 1969 bridge pier.
Pier no. 2 was founded on shale, with a small portion of the downstream end of the pier supported on clay. Although shale and sandstone are not an ideal foundation material, this material can provide a strong or competent foundation if continuous and confined. Pier no. 2 was built circa 1897 and extended in 1912, so the shale and sandstone material supporting the pier was competent and confined for over a century before the force of the flood broke it up.
Bridge inspection and maintenance
Bridges are critical pieces of a railroad's infrastructure that require frequent and comprehensive inspection and maintenance. The regular inspection and maintenance protocols of Canadian Pacific Railway's (CP's) Railway Bridge Safety Management program (RBSMP) closely reflect Transport Canada's (TC's) Guideline for Bridge Safety Management. Inspections conducted on the Bonnybrook Bridge exceeded regulatory requirements during the flood.
Routine visual inspections of the pier foundations during low water flows were conducted as part of annual inspections. During the recent visual inspections of the Bonnybrook Bridge, there was no evidence of foundation scour.
CP took measures during the flood to ensure that the bridge was stable by placing loaded cars on the deck and increasing visual inspections from ground level. Visual observations of any deviations in the rail and track alignment or surface would have indicated the gradual settlement of a bridge pier; however, they would not necessarily have provided warnings of an impending bridge failure.
Underwater inspections during the flood were not feasible due to the high volume of fast-moving, turbid water. The full extent of the scour was not determined until about 2 months after the bridge failure, when visual inspections and sonar surveys were conducted. During the flood, CP believed that train operations over the bridge were safe, as there had been no changes in the bridge geometry and the bridge had no history of foundational instability or scour.
Even prior to the occurrence, track speed was limited to 10 mph over the bridge on the 3 non-main tracks and 25 mph on the main track, P1. Less than 1.5 hours before the collapse, the bridge was safely used by a loaded potash train on track P1. Due to the extent of scour and loss of foundation support that was caused by the flood waters but was unknown to the bridge inspectors, the bridge failed.
Bridges with spread footings
Most of the CP bridges in southern Alberta, including the ones with spread footings, are decades old and have withstood major flooding in the past. Adequate protection against flood damage and washouts is essential for maintaining dependable service and avoiding the significant costs involved in replacing damaged structures and restoring operations. Placing of rip-rap is commonly used to inhibit local scour at bridge piers and abutments. If measures are not taken to inhibit local scour, especially at bridges with spread footing foundations, there is an increased risk that high-water events will lead to bridge failures.
When derailments involving dangerous goods occur in rural areas, CP usually takes the lead role in the emergency response. In these situations, CP personnel will have more experience and technical knowledge in dealing with the dangerous goods involved than will small rural fire departments, which are normally staffed with volunteer personnel.
The Bonnybrook incident occurred in Calgary, a major city with comprehensive emergency response resources. For this reason, the city fire department assumed overall command of the response, even though its resources were heavily deployed under the city's state of emergency due to the flood. The unified command structure initiated by the City of Calgary Fire Department worked well, including in its interaction with CP, in securing the site and in developing and executing the plan to safely remove the derailed cars from the bridge.
Findings as to causes and contributing factors
Findings as to risk
Safety action taken
On 28 June, Transport Canada (TC) issued an emergency directive to Canadian Pacific Railway (CP) under Section 33 of the Railway Safety Act. The directive ordered CP to identify the bridges located in the South Saskatchewan River Basin (SSRB), Oldman River, Bow River, and Red Deer River basins that have spread footings, and to restrict train speed over these bridges to 10 mph. Train speed over a bridge was not to be increased unless the bridge was inspected by a professional engineer or by a qualified bridge inspector under the direction of a professional engineer, and unless the bridge was determined to be safe for train operations. Within 48 hours of removal of the speed restriction, CP was requested to provide written confirmation to TC that the bridge was safe to operate over based on the assessment of the qualified bridge inspector and the determination of the professional engineer. The directive remained in effect until 28 December 2013.
In addition, TC
TC is updating its Guideline for Bridge Safety Management and Guideline for Culvert Safety Management. Scour, erosion, and stream stability hazards, including those associated with spread foundations, will be addressed. In June 2014, TC met with railway industry representatives to discuss the proposed revisions. The revised guidelines are expected to be finalized by December 2014. CP identified 56 bridges with spread footings that were situated within the designated river basins. Bridges at Mile 0.30 of the Brooks Subdivision and Mile 27.3 of the Macleod Subdivision had speed restrictions of 10 mph imposed due to scour and wing-wall failure, respectively. CP indicated that the repair work was completed during summer 2013. Underwater inspections and tactile inspections of the bridges at Mile 19.8 and Mile 74.9 of the Crowsnest Subdivision and Mile 51.8 of the Laggan Subdivision were conducted.
In addition, CP
This report concludes the Transportation Safety Board's investigation into this occurrence. The Board authorized the release of this report on 05 November 2014. It was officially released on 17 December 2014.
Appendix A – Estimated peak river flowsFootnote 18
Note: m³/sec = cubic metres per second
Bow River at Banff
2013 estimated peak flow: 439 m³/sec
2012 peak flow: 268 m³/sec
1923 peak flow: 399 m³/sec
Bow river at Calgary
2013 estimated peak flow: 1740 m³/sec (21 June 2013)
2005 peak flow: 791 m³/sec
1932 peak flow: 1520 m³/sec
Crowsnest River at Frank
2013 estimated peak flow: 133 m³/sec
1998 peak flow: 75 m³/sec
1995 peak Flow: 135 m³/sec
Elbow River at Bragg Creek
2013 estimated peak flow: 959 m³/sec
1932 peak flow: 836 m³/sec
1929 peak flow: 489 m³/sec
Oldman River at Lethbridge
2013 estimated peak flow: 2670 m³/sec
1995 peak flow: 4670 m³/sec
Red Deer River at Drumheller
2013 estimated peak flow: approximately 1300 m³/sec (near midnight on Sunday, 23 June 2013)
Sheep River at Black Diamond
2013 estimated peak flow: 720 m³/sec
2005 peak flow: 380 m³/sec
Sheep River at Okotoks
2013 estimated peak flow: over 1000 m³/sec
2005 peak flow: 769 m³/sec
South Saskatchewan River at Medicine Hat
2013 estimate peak flow: 5300 m³/sec (early morning on Monday, 24 June 2013)
Appendix B – Sonar images of scour
- Footnote 1
All times are Mountain Daylight Time (Coordinated Universal Time minus 6 hours).
- Footnote 2
DOT-111A tank cars are non-pressure, general-purpose cars with or without insulation. DOT-111S tank cars are non-pressure, general-purpose cars with head shields. AAR211A tank cars are equivalent to DOT-111A cars, except that they are not used to transport regulated commodities.
- Footnote 3
The material safety data sheet (MSDS) indicates that Durasyn 125 (polyalphaolefin) is not classified as hazardous for transport.
- Footnote 4
The failed bridge was demolished and rebuilt.
- Footnote 5
On a bridge, the superstructure is the portion of the structure supported by abutments and by a pier or piers and that directly receives the live load (trains).
- Footnote 6
Spread footings are footings founded directly on the shale bedrock below the alluvial sediment in the river bottom, without piling or socketing.
- Footnote 7
The headwaters of the Bow River are in the Rocky Mountains, upstream of Lake Louise. Although there are a number of storage reservoirs in the basin upstream of Calgary, their primary purpose is to provide hydroelectric power, and therefore, they offer little opportunity to moderate flood flows.
- Footnote 8
Rip-rap refers to large stones that are used to prevent water erosion.
- Footnote 9
All city bridges are either sitting on (or socketed into) the bedrock or on piles/caissons down to the bedrock. The city has no river bridges with spread footings founded directly on the shale bedrock below the alluvial sediment in the river bottom, similar to CP’s Bonnybrook Bridge. Confirmation of the channel scour was deemed necessary to a full assessment of bridge conditions, and the city initiated an underwater inspection assignment, which was conducted in summer 2013.
- Footnote 10
Description adapted from RadHyPS [online], RailWIS (2008), available at http://www.radhyps.com/RailWIS.htm (last accessed on 14 November 2014).
- Footnote 11
Description of regulatory oversight of railway bridge safety as provided in a letter from Transport Canada Rail Safety Director General Luc Bourdon to TSB Chair Wendy Tadros (25 July 2014).
- Footnote 12
“Crossing” refers to the area where the bridge crosses the river.
- Footnote 13
Bathymetry is the study of the “beds” or “floors” of water bodies, including the ocean, rivers, streams, and lakes.
- Footnote 14
Association of American Railroads
- Footnote 15
CANUTEC is the Canadian Transport Emergency Centre, operated by the Transportation of Dangerous Goods (TDG) Directorate of Transport Canada. The directorate’s overall mandate is to promote public safety in the transportation of dangerous goods by all modes.
- Footnote 16
CHEMTREC serves as a round-the-clock resource for obtaining immediate critical-response information for incidents involving hazardous materials and dangerous goods. CHEMTREC is linked to the largest network of chemical and hazardous material experts in the world, including chemical and response specialists, public emergency services, and private contractors.
- Footnote 17
Reacher cars are cars used to facilitate a coupling to other cars over a distance of track where it is desirable that the track not be subjected to the weight of a locomotive. Reacher cars are normally empty or lightly loaded.
- Footnote 18
Government of Alberta Estimated Peak River Flows: Forecasted flows are based on the best information available. Estimated peak flows are preliminary recorded data. The data were provided by the Water Survey of Canada.
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